Conventionally, a sample analyzer for aspirating liquid by an aspirating tube from a container accommodating the liquid such as sample or reagent is known (see e.g., Japanese Laid-Open Patent Publication No. 2009-180605).
For the purpose of efficient reagent aspirating process, the sample analyzer disclosed in Japanese Laid-Open Patent Publication NO. 2009-180605 sets a lowering speed switching height for switching a speed of lowering a reagent aspirating nozzle by adding a margin value to a height of a reagent in a reagent bottle, lowers at high speed the reagent nozzle to the lowering speed switching height, and lowers at low speed the reagent nozzle from the lowering speed switching height to the reagent in the reagent bottle. In the sample analyzer disclosed in Japanese Laid-Open Patent Publication NO. 2009-180605, an initial liquid level of the reagent in the reagent bottle is stored in a memory in advance according to a type of the reagent bottle. Unless an aspiration of the reagent has been performed from the reagent bottle, the lowering speed switching height is set using the initial liquid level stored in the memory. Then the reagent nozzle is lowered at high speed to the set lowering speed switching height, and the reagent nozzle is lowered at low speed from the lowering speed switching height.
However, in the sample analyzer disclosed in Japanese Laid-Open Patent Publication No. 2009-180605, the size of the reagent bottle varies due to machining error of the reagent bottle or the like even with the same type of the reagent bottle, and thus an actual initial liquid level may differ from the initial liquid level stored in the memory and the reagent nozzle may enter into the reagent while lowering at high speed. To prevent this, the margin value used for a setting of the lowering speed switching height needs to be greatly ensured. As a result, the lowering speed switching height is set at a high position. Therefore, it may become difficult to perform a reagent aspirating operation rapidly.
In view of such aspects, it is a main object of the present invention to provide a sample analyzer and a liquid aspirating method enabling to perform a liquid aspirating operation more rapidly than the prior art when a liquid level is unknown.